Business Segments (Goodwill and Intangible Assets by Geographic Area) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Schedule of Goodwill and Intangible Assets by Geographic Areas [Line Items]
Intangible assets, net (including goodwill)	$ 3,085,793	$ 3,401,014
United States
Schedule of Goodwill and Intangible Assets by Geographic Areas [Line Items]
Intangible assets, net (including goodwill)	2,971,753	3,278,021
Rest of world
Schedule of Goodwill and Intangible Assets by Geographic Areas [Line Items]
Intangible assets, net (including goodwill)	$ 114,040	$ 122,993